<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>纹理转场</title>
    <style>
        body {
            margin: 0;
            overflow: hidden
        }
    </style>
</head>

<body>
<canvas id="canvas"></canvas>
<script id="vertexShader" type="x-shader/x-vertex">
    attribute vec4 a_Position;
    attribute vec2 a_Pin;
    varying vec2 v_Pin;
    void main(){
      gl_Position = a_Position;
      v_Pin=a_Pin;
    }
  </script>
<script id="fragmentShader" type="x-shader/x-fragment">
    precision mediump float;
    uniform sampler2D u_Sampler;
    uniform sampler2D u_Pattern;
    uniform float u_Ratio;
    varying vec2 v_Pin;
    void main(){
      vec4 o=texture2D(u_Sampler,v_Pin);
      vec4 p=texture2D(u_Pattern,v_Pin);
      gl_FragColor=mix(o,p,u_Ratio);
    }
  </script>
<script type="module">
  import Track from "../jsm/Track.js";
  import { imgPromise, initShaders, } from '../jsm/Utils.js';
  import Poly from './jsm/Poly.js';

  const canvas = document.getElementById('canvas');
  canvas.width = window.innerWidth;
  canvas.height = window.innerHeight;
  const gl = canvas.getContext('webgl');

  const vsSource = document.getElementById('vertexShader').innerText;
  const fsSource = document.getElementById('fragmentShader').innerText;
  initShaders(gl, vsSource, fsSource);
  gl.clearColor(0.0, 0.0, 0.0, 1.0);

  //数据源
  const source = new Float32Array([
    -0.4, 0.8, 0, 1,
    -0.4, -0.8, 0, 0,
    0.4, 0.8, 1, 1,
    0.4, -0.8, 1, 0,
  ]);

  let n = 0
  let len = 5
  const obj = { ratio: 0 }
  let track = null

  const rect = new Poly({
    gl,
    source,
    type: 'TRIANGLE_STRIP',
    uniforms: {
      u_Ratio: {
        type: 'uniform1f',
        value: obj.ratio
      }
    },
    attributes: {
      a_Position: {
        size: 2,
        index: 0
      },
      a_Pin: {
        size: 2,
        index: 2
      },
    }
  })

  loadImg()

  function loadImg() {
    n++;
    const i1 = n % len
    const i2 = (n + 1) % len

    const originImg = new Image()
    originImg.src = `./images/pattern${i1}.jpg`

    const pattern = new Image()
    pattern.src = `./images/pattern${i2}.jpg`

    Promise.all([
      imgPromise(originImg),
      imgPromise(pattern),
    ]).then(() => {
      changeImg(originImg, pattern)
      ani()
    })
  }

  function changeImg(...imgs) {
    obj.ratio = 0

    rect.maps = {
      u_Sampler: { image: imgs[0] },
      u_Pattern: { image: imgs[1] },
    }
    rect.updateMaps()
    track = new Track(obj);
    track.start = new Date();
    track.timeLen = 1500;
    track.onEnd = loadImg
    track.keyMap = new Map([
      [
        "ratio",
        [
          [0, 0],
          [700, 1]
        ],
      ],
    ]);
  }


  /* 动画 */
  function ani() {
    track.update(new Date())
    rect.uniforms.u_Ratio.value = obj.ratio;
    rect.updateUniform()
    render()
    requestAnimationFrame(ani)
  }

  //渲染
  function render() {
    gl.clear(gl.COLOR_BUFFER_BIT);
    rect.draw()
  }
</script>
</body>

</html>
